JP7370919B2 - How to extract Sc - Google Patents

Description

The present invention relates to a method for extracting Sc.

As a method for separating Sc from a solution containing scandium (Sc), it is preferable to remove impurities as much as possible. As such a technique, Patent Document 1 discloses a method that focuses on thorium (Th) as an impurity and performs leaching and/or neutralization under specific conditions to effectively separate Sc and Th. There is.

JP 2018-150588 Publication

When attempting to extract Sc from a solution containing Sc by solvent extraction, a cladding, which is a third phase, may be generated in addition to the organic phase and the aqueous phase. There is a problem in that the crud generated by solvent extraction also incorporates useful metal components, reducing the recovery rate of metal components. Additionally, the extractant may be incorporated into the cladding, which poses a major cost problem if the extractant is expensive. Furthermore, the generated crud may impede phase separation between the organic phase and the aqueous phase, making it impossible to perform the solvent extraction operation normally. Therefore, there is a need for a method for extracting Sc that can minimize the generation of crud when attempting to extract Sc from a solution containing Sc by solvent extraction.

In view of the above circumstances, an object of the present invention is to provide a method for extracting Sc that can satisfactorily suppress the generation of crud when extracting Sc from a solution containing Sc by solvent extraction.

As a result of intensive research, the present inventors have found that by performing solvent extraction under specific conditions, it is possible to provide a method for extracting Sc that can satisfactorily suppress the generation of crud. Based on these findings, the present invention is specified as follows.

(1) A step of adding D2EHPA to a solution containing Sc to extract Sc into an organic phase,
In the organic phase, the ratio of the concentration A (mol/l) of D2EHPA to the concentration B (mol/l) of Sc is A/B>6,
A method for extracting Sc, characterized in that the extraction temperature is 30°C or higher.
(2) The method for extracting Sc according to (1), wherein the concentration of D2EHPA in the organic phase is less than 0.3 (mol/l).
(3) The method for extracting Sc according to (1) or (2), wherein the pH during extraction is -0.5 to 0.5.
(4) If crud occurs in the extract due to the extraction,
A step of separating the extract into solid-liquid;
leaching the solid-liquid separated cladding with an organic solvent containing D2EHPA;
Scrubbing the leached liquid obtained by leaching with the organic solvent with an acid;
The method for extracting Sc according to any one of (1) to (3), comprising the step of adding a strong alkaline solution to the solvent after the scrubbing to obtain crude Sc(OH) ₃ .
(5) Extraction of Sc according to (4), wherein the organic solvent containing D2EHPA contains D2EHPA in a mole number that is 10 times or more and less than 20 times the total mole number of Sc and Fe in the cladding. Method.
(6) Sc according to (4) or (5), characterized in that in the step of leaching the solid-liquid separated cladding with an organic solvent containing D2EHPA, the temperature of the organic solvent is 40°C or higher. extraction method.
(7) The solution containing the Sc is
A step of leaching Sc from a raw material containing Sc, and
The Sc according to any one of (1) to (6), which is a neutralized liquid obtained by performing a step of neutralizing the leached liquid obtained by leaching the Sc. extraction method.

According to the present invention, it is possible to provide a method for extracting Sc that can satisfactorily suppress the generation of crud when extracting Sc from a solution containing Sc by solvent extraction.

3 shows a recovery flow of Sc in an embodiment of the present invention. 3 shows a processing flow of cladding in an example.

Hereinafter, specific embodiments for implementing the present invention will be described. The following description is provided to facilitate understanding of the invention. That is, it is not intended to limit the scope of the present invention.

<Raw materials>
Embodiments of the present invention relate to a method for recovering Sc from a raw material containing Sc. In one embodiment, the raw material containing Sc may be an ore containing Sc. In a further embodiment, the ore containing Sc may be an ore containing Sc and Th. In a further embodiment, the ore containing Sc may be a titanium ore that is a raw material for refining titanium (Ti). In a further embodiment, the raw material containing Sc may be a chlorinated residue produced when refining Ti. In the following, a case where the raw material containing Sc is a chloride residue will be described as an example of the raw material, although it is not limited thereto.

<Refining of titanium>
Conventionally, titanium has generally been refined from titanium ore by the Kroll method. Titanium ore and coke are charged into a fluidized bed reactor. Then, chlorine gas is injected from the lower part of the fluidized bed reactor. Titanium ore reacts with chlorine gas to produce titanium tetrachloride. Titanium tetrachloride is in a gaseous state at the temperature within the reactor. This gaseous titanium tetrachloride is sent to the next cooling system and cooled down. The cooled titanium tetrachloride becomes liquid and is recovered.

<Chloride residue>
When gaseous titanium tetrachloride is sent to the next cooling system, fine powder impurities are carried along with the airflow. The impurities include substances other than titanium (iron, scandium, vanadium, niobium, zirconium, aluminum, silicon, thorium, etc., some of which are chlorides), unreacted ores, unreacted coke, and the like. These impurities are recovered in solid form in the cooling system. This recovered material is referred to herein as chlorinated residue. The chlorinated residue may be made into a slurry or may be in the form of a group of dry particles. Typically, valuable metals can be recovered using a slurry.

<Quality of chloride residue>
The chlorinated residue obtained in the above-mentioned process has various rare metals and may contain useful elements such as Sc, V, Nb, Zr, Y, La, Ce, Pr, and Nd. There is. If these can be recovered, profits can be increased using the recovered materials. Although the present invention is not limited to the following theory, since chloride residue is a mixture produced in the process of titanium smelting, many of its constituent components are derived from titanium concentrate. Titanium concentrate can be obtained by subjecting excavated titanium ore to flotation, magnetic separation, specific gravity beneficiation, etc. to increase the Ti grade. Therefore, it is thought that the target Ti-containing particles tend to form relatively large particles.On the other hand, other rare metal elements that are impurities in Ti concentrate are formed as fine particles during the manufacture of Ti concentrate. It is thought that it is attached to the concentrate and mixed in.

<Pretreatment of chloride residue>
The above-mentioned chloride residue is in a high temperature state immediately after being recovered during titanium smelting, and needs to be cooled before performing a process to recover valuable metals. The cooling method is not particularly limited, and cooling may be performed by means such as air cooling or water cooling.

Further, it is preferable to wash the chlorinated residue with water before performing the classification described below. This is because water-soluble impurities such as FeCl ₂ can be removed by washing with water. In addition, if it is washed with water, the above-mentioned cooling treatment can be performed at the same time.

<Recovery of Sc>
An overview of Sc recovery in one embodiment is shown in FIG. Each step will be specifically explained below.

(1) Sc leaching process (Figure 1 “Leaching”)
In one embodiment, the method of the invention includes leaching Sc from a feedstock containing Sc using an acidic solution. The pH of the acidic solution is preferably adjusted to a range of 0.3 to 0.9 after leaching (or at the end of leaching). If it is less than 0.3, the amount of leached thorium will also increase, which will hinder separation from scandium. If it exceeds 0.9, the amount of scandium leached will decrease.

Further, the temperature during the leaching step is not particularly limited, but the temperature of the acidic solution is preferably 60 to 90°C, more preferably 80 to 90°C. When the temperature is lower than 60°C, if Th is contained, it becomes difficult to see a difference in the amount of leaching between Sc and Th, making separation difficult. The higher the temperature, the lower the amount of thorium leached, so the higher the leaching temperature is, the better. However, for reasons such as boiling of the solution, the typical upper limit may be 90°C.
The time for the leaching reaction is not particularly limited, but may be at least 1 hour or more, typically 2 hours or more. The upper limit is also not particularly limited, but is typically 24 hours or less.
Further, the pulp concentration is not particularly limited, but may be 100 to 600 g/L, typically 200 to 500 g/L.

The components for achieving the above acidic range are not particularly limited, but strong acids can be used. For example, hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, bromic acid, mixtures thereof, etc. can be used. The amount is not particularly limited, but it may be added in an amount that can achieve the above pH range.

(2) Neutralization process of leachate (Figure 1 "Neutralization")
In one embodiment, the method of the invention can include a neutralization step to adjust the pH of the solution after leaching. That is, it can include a step of adjusting the pH to be more alkaline than during leaching. Thereby, Th can be precipitated while leaving Sc in the solution.

The pH range in the neutralization step is preferably 1.3 to 2.5. When it is less than 1.3, precipitation of Th is difficult to occur. On the other hand, when the pH exceeds 2.5, the amount of Th precipitated does not increase, but rather Th also begins to precipitate. A more preferred range is a pH of 1.8 to 2.3. Thereby, most of Th can be precipitated without losing Sc due to precipitation.

In adjusting the pH in the neutralization process, the pH is adjusted to be more alkaline than during leaching, so NaOH, Na ₂ CO ₃ , CaO, Ca(OH) ₂ , CaCO ₃ , LiOH, Li ₂ CO ₃ , KOH , K ₂ CO ₃ , Mg(OH) ₂ , MgCO ₃ and the like are preferably used. The amount is not particularly limited, but it may be added in an amount that can achieve the above-mentioned pH range.

From the viewpoint of operational simplicity, leaching and neutralization are preferably carried out in the same tank. Of course, it is also possible to perform solid-liquid separation ("solid-liquid separation A" in FIG. 1) immediately after leaching (before neutralization), and to perform leaching and neutralization in different tanks.

(3) Solid-liquid separation (Figure 1 "Solid-liquid separation B")
After the precipitate is formed, solid-liquid separation can be performed. By collecting the solution side containing a large amount of Sc, the contamination of Th can be reduced (as described above, Th mainly moves to the precipitation side). The solid-liquid separation method is not particularly limited, and known methods such as filtration can be used.

(4) Sc extraction After the step of solid-liquid separation B, Sc is recovered from the neutralized liquid using an organic solvent. More specifically, when the neutralized solution is subjected to solvent extraction using TBP as an extractant, Fe moves to the organic phase side and other rare metals such as Sc remain in the aqueous phase side. Regarding the organic phase side, Fe back extraction is performed, and the liquid after Fe back extraction is discarded as waste water. Note that if the Fe content in the raw material is low and the amount of Fe leached is low, this Fe extraction step may be omitted.

On the other hand, the aqueous phase is subjected to solvent extraction using D2EHPA (Bis(2-ethylhexyl) phosphate) as an extractant ("Sc extraction" in FIG. 1). As a result, Sc moves to the organic phase side, while some elements other than Sc (for example, Nb, Y, La, Ce, Zr, Pr, or Nd) move to the aqueous phase side (after Sc extraction). liquid). The liquid after Sc extraction can be used to recover elements other than Sc. The "Sc extraction" will be described in more detail below.

In "Sc extraction", D2EHPA (Bis(2-ethylhexyl) phosphate) is added to a solution containing Sc (the above-mentioned aqueous phase) to extract Sc into the organic phase. Here, the amount of D2EHPA added is controlled so that the ratio of the concentration A (mol/l) of D2EHPA to the concentration B (mol/l) of Sc in the organic phase is A/B>6. Generally, 6 mol of D2EHPA coordinates with 1 mol of Sc and is extracted, but if D2EHPA is less than 6 mol, Sc will not dissolve in the organic phase and will precipitate as a solid. This means that not only Sc loss but also D2EHPA loss occurs due to cladding generation. On the other hand, the amount of D2EHPA added is controlled so that the ratio of the concentration A (mol/l) of D2EHPA to the concentration B (mol/l) of Sc in the organic phase is A/B>6. Therefore, the generation of crud can be effectively suppressed. The ratio of the concentration A (mol/l) of D2EHPA to the concentration B (mol/l) of Sc in the organic phase is preferably A/B>8, more preferably A/B>12. . The upper limit value of A/B is preferably A/B<16 from the viewpoint of suppressing the extraction of impurities such as Th and from the viewpoint of reducing the amount of organic solvent to be handled.

Furthermore, the extraction temperature during solvent leaching is controlled to 30°C or higher. Thereby, the generation of crud can be effectively suppressed. The extraction temperature during solvent leaching is preferably 30°C or higher, more preferably 35°C or higher. The upper limit of the extraction temperature during the solvent leaching is preferably 50° C. or less from the viewpoint of suppressing volatilization of the organic phase.

It is preferred that the concentration of D2EHPA in the organic phase is less than 0.3 (mol/l). As a result, when the solution containing Sc contains Th, the extraction of Th can be suppressed well, and the incorporation of impurities can be prevented. More preferably, the concentration of D2EHPA in the organic phase is less than 0.22 (mol/l). On the other hand, if the concentration of D2EHPA in the organic phase is too low, the extraction equipment must be enlarged. From this viewpoint, the concentration of D2EHPA in the organic phase is preferably 0.15 (mol/l) or more.

The pH during solvent extraction is preferably adjusted to a range of -0.5 to 0.5. By adjusting the pH during solvent extraction within such a range, the generation of crud can be better suppressed. Further, when Sc is extracted in the pH range, the concentration of impurities co-extracted into the organic phase is preferably less than 0.1 mol/L, more preferably less than 0.05 mol/L.

(5) Scrub process, Sc back extraction, calcination If crud is generated in the extracted liquid when the neutralized liquid is extracted with an organic solvent, solid-liquid separation is performed in the process of solid-liquid separation of the extracted liquid. The resulting cladding is leached with an organic solvent containing D2EHPA, and then the leached liquid obtained by leaching with the organic solvent is scrubbed with an acid (FIG. 1 "Scrubbing"). This makes it possible to reduce the amount of Fe, Th, and the like mixed in. A strongly alkaline solution can then be added to the scrubbed solvent to obtain crude Sc(OH) ₃ .

Examples of acids used at this time include HCl, NaCl, H ₂ SO ₄ and the like of about 1M to 4.2M. Further, examples of the strong alkaline solution used include 1.5 to 2.5M aqueous solutions such as NaOH or KOH. If the concentration of the strong alkaline solution is less than 1.5M, the organic phase may become cloudy, and if it exceeds 2.5M, it may be difficult to filter using a filter aid such as cellulose powder. .

At this time, it is preferable that the organic solvent containing D2EHPA contains D2EHPA in an amount of 10 times or more and less than 20 times the total number of moles of Sc and Fe in the cladding. According to such a configuration, it is possible to satisfactorily dissolve the generated crud. At this time, it is more preferable that the organic solvent containing D2EHPA contains D2EHPA in a mole number that is 12 times or more and less than 18 times the total mole number of Sc and Fe in the cladding.

Further, in the above-described step of leaching the solid-liquid separated cladding with an organic solvent containing D2EHPA, the temperature of the organic solvent is preferably 40° C. or higher. According to such a configuration, it is possible to satisfactorily dissolve the generated crud. Further, in the step of leaching the solid-liquid separated cladding with an organic solvent containing D2EHPA, it is more preferable that the temperature of the organic solvent is 45° C. or higher. Further, from the viewpoint of suppressing volatilization of the organic phase, the temperature is preferably 50° C. or lower.

On the other hand, for the organic phase side after scrubbing, for example, perform crystallization stripping with an alkaline aqueous solution such as NaOH (Figure 1 "Sc back extraction") to obtain a scandium hydroxide slurry, and filter the scandium hydroxide slurry. After calcination (FIG. 1 "Solid-liquid separation C" and "Calcination"), the final product can be recovered in the form of Sc ₂ O ₃ . Alternatively, the obtained Sc(OH) ₃ can be leached, scandium can be precipitated in the form of scandium carboxylate using a carboxylic acid such as oxalic acid, and further calcined to recover it in the form of Sc ₂ O ₃ . can.

(6) Classification step In one embodiment, the raw material containing Sc may be a chlorinated residue as described above. In this embodiment, after washing the chlorinated residue with water, the chlorinated residue can be classified into coarse particles and fine particles. The classification method is not particularly limited, and may be dry or wet. More preferred is a wet method. This is because when the chloride residue is washed with water, there is no need for drying it. Furthermore, as a method of classification, a sieve with a specific size of openings may be used. As the wet classification, a hydraulic classifier, a horizontal water classifier, or a centrifugal sedimentator may be used. As the dry classification, an air separator or an air classifier may be used.

The standard value for classification is not particularly limited, and a size range that contains a large amount of rare metals (for example, Sc, V, Nb, Zr, Y, La, Ce, Pr, or Nd) may be adopted as the upper limit. . For example, the upper limit of the reference value may be 55 μm or less, 40 μm or less, or 25 μm or less. The lower limit of the reference value may be 10 μm or more, 15 μm or more, or 20 μm or more. As a result, for example, at least about 82% (when the reference value is set to 25 μm), about 84% (when the reference value is set to 38 μm), or about 88% (when the reference value is set to 38 μm) of the Sc present in the chloride residue. 53 μm) can be recovered. On the other hand, the amount of materials to be collected can be reduced. Furthermore, many of the other impurities (eg, Fe, coke, unreacted titanium, etc.) are distributed to the coarse grain side.

When using a sieve as the classification means, the size of the mesh can be appropriately determined based on the classification standard value. For example, when classifying using 25 μm as a reference value, a mesh size of 25 μm (500 mesh according to the JIS standard) is used. Then, the material that passes through the sieve is treated as fine particles, and the material that remains on the sieve is treated as coarse particles.

The fine particles obtained after classification can be subjected to a leaching process under the conditions described above to recover Sc.

Hereinafter, more specific examples will be disclosed to facilitate understanding of the present invention.

(Test example 1)
After neutralization, the solution was mixed with an organic solvent containing extractant (D2EHPA): 10% by volume, modifier (TBP): 5% by volume, and diluent (Shellsol D70): 85% by volume, and the concentration of D2EHPA was adjusted to A (mol/mol/%). l) and the concentration B (mol/l) of Sc was extracted under conditions such that A/B = 5. Since crud was generated, the crud recovered by solid-liquid separation was subjected to the following procedure. Processed.
The leaching conditions for the cladding are shown in Table 1. In Table 1, "PD" indicates the amount of cladding added per liter of organic solvent, and "wet" indicates that the cladding is in a wet state containing water and oil. In addition, the leaching was carried out at two temperatures: 10°C and 40°C.

When leaching was carried out at a leaching temperature of 10°C, undissolved residue was observed. On the other hand, when leaching was carried out at a leaching temperature of 40°C, the entire amount was dissolved. It is thought that this causes the solubility of the cladding to increase as the temperature rises, like the solubility of ordinary inorganic salts in water.

Further, the entire amount of generated crud was processed according to the flow shown in FIG. 2. In this way, Sc and the organic phase were recovered. Each quantity is indicated in the figure. From the recovered Sc amount and each concentration in the scrubbing liquid, the quality of the cladding was estimated to be: Sc: 1% by mass, Fe 1% by mass, and D2EHPA: about 50% by mass.

The specific embodiments of the present invention have been described above. The above embodiments are merely specific examples of the present invention, and the present invention is not limited to the above embodiments. For example, technical features disclosed in one of the embodiments described above may be provided in other embodiments. Furthermore, for a particular method, it is also possible to replace some of the steps with the order of other steps, and a further step may be added between two specific steps. The scope of the invention is defined by the claims.

Claims (6)

A step of adding D2EHPA to a solution containing Sc to extract Sc into an organic phase,
In the organic phase, the ratio of the concentration A (mol/l) of D2EHPA to the concentration B (mol/l) of Sc is A/B>6,
The concentration of D2EHPA in the organic phase is less than 0.3 (mol/l),
A method for extracting Sc, characterized in that the extraction temperature is 30°C or higher. The method for extracting Sc according to claim 1, wherein the pH at the time of extraction is -0.5 to 0.5. When crud occurs in the extract due to the extraction,
A step of separating the extract into solid-liquid;
leaching the solid-liquid separated cladding with an organic solvent containing D2EHPA;
Scrubbing the leached liquid obtained by leaching with the organic solvent with an acid;
3. The method for extracting Sc according to claim 1 , further comprising the step of adding a strong alkaline solution to the scrubbed solvent to obtain crude Sc(OH) ₃ . 4. The method for extracting Sc according to claim 3 , wherein the D2EHPA-containing organic solvent contains D2EHPA in a mole number that is 10 times or more and less than 20 times the total mole number of Sc and Fe in the cladding. 5. The method for extracting Sc according to claim 3 , wherein in the step of leaching the solid-liquid separated cladding with an organic solvent containing D2EHPA, the temperature of the organic solvent is 40° C. or higher. The solution containing the Sc is
A step of leaching Sc from a raw material containing Sc, and
Sc according to any one of claims 1 to 5, wherein the Sc is a neutralized liquid obtained by performing a step of neutralizing the leached liquid obtained by leaching the Sc. extraction method.